The present invention relates to water distributing installation controllers for controlling distributing reservoirs in water-supply installations.
Distributing reservoirs serve to receive water from filtration plants and distribute it to a distributing area in accordance with a demand thereof. The distributing reservoirs need to provide the function of adjusting temporal variations in the water delivery and the function of maintaining a predetermined water quantity and pressure even upon an accident which occurs upstream thereof, etc. As for the distributing reservoirs, refer to Plan and Description of Water-Supply Installations, page 369, 1990 edition, compiled under the supervision of the Ministry of Welfare. On the other hand, due to its operation based on the estimated maximum one-day water consumption, the filtration plants supply to the distributing reservoirs a given quantity of clear water per hour. Control of the distributing reservoirs needs to satisfy the above two requirements in the well-balanced way. Typical examples of this control are control at the constant water level and control at a target water level set every hour.
FIG. 21 shows a water distributing installation wherein known distributing-reservoir water-level control is applied to pumps-number control. Referring to FIG. 21, a distributing reservoir 1 is provided with a level gauge 2 for measuring the level of water therein. Water pumps 3 are arranged to supply water from a clear-water reservoir to the distributing reservoir 1. The water pumps 3 are controlled by a pump start/stop command derived from a pumps-number control part 4. The pumps-number control part 4 determines the number of pumps 3 operated by a signal derived from the level gauge 2.5 designates a duct network of a distributing area.
With the water distributing installation having the above structure, when the water level of the distributing reservoir 1 is higher than a highest set water level HWL, all of the pumps 3 are stopped. On the other hand, when the water level is the following, the number of pumps 3 operated is controlled as follows:
When the water level is higher than a first controlled water level LT1, the number of pumps 3 is determined to one by the following formula: EQU LT1=((HWL-LWL)/5).times.1-HWL
where LWL is a lowest set water level.
When the water level is higher than a second controlled water level LT2, the number of pumps 3 is determined to two by the following formula: EQU LT2=((HWL-LWL)/5).times.2-HWL
When the water level is higher than a three controlled water level LT3, the number of pumps 3 is determined to third by the following formula: EQU LT3=((HWL-LWL)/5).times.3-HWL
When the water level is higher than a fourth controlled water level LT4, the number of pumps 3 is determined to four by the following formula:
LT4=((HWL-LWL)/5).times.4-HWL
When the water level is higher than a fifth controlled water level LT5, the number of pumps 3 is determined to five by the following formula: EQU LT4=((HWL-LWL)/5).times.5-HWL
FIG. 22 shows a water distributing installation wherein known distributing-reservoir water-level control is applied to valve-opening control. Referring to FIG. 22, a distributing reservoir 1 is provided with a level gauge 2 for measuring the level of water therein. There is arranged a water valve 6 controlled in opening degree when supplying water from a clear-water reservoir to the distributing reservoir 1. The water valve 6 is controlled by a valve-opening change command derived from a water-valve control part 7. The water-valve control part 7 determines the opening degree of the water valve 6 by a signal derived from the level gauge 2. 8 designates a distribution pump.
With the water distributing installation having the above structure, when the water level of the distributing reservoir 1 is higher than the highest set water level HWL, the water valve 6 is closed, whereas when the water level is higher than LT1, the water valve 6 is put in the 50% opening degree. It is noted that LT1 is determined by the following formula: EQU LT1=((HWL-LWL)/5).times.1-HWL
Likewise, when the water level is higher than LT2, the water valve 6 is put in the 55% opening degree. when the water level is higher than LT3, the water valve 6 is put in the 60% opening degree. When the water level is higher than LT4, the water valve 6 is put in the 65% opening degree. The corresponding formulae are as follows: EQU LT2=((HWL-LWL)/5).times.2-HWL EQU LT3=((HWL-LWL)/5).times.3-HWL EQU LT4=((HWL-LWL)/5).times.4-HWL
On the other hand, when the water level is lower than LT4, the water valve 6 is put in the 70% opening degree.
FIG. 23 shows a water distributing installation wherein known distributing-reservoir water-level control is applied to pumps-number control for a chlorine mixing reservoir. Referring to FIG. 23, a distributing reservoir 1 is provided with a level gauge 2 for measuring the level of water therein. Water pumps 3 are arranged to supply water from a chlorine mixing reservoir 9 to the distributing reservoir 1. The water pumps 3 are controlled by a pump start/stop command derived from a pumps-number control part 4. The pumps-number control part 4 determines the number of pumps operated by a signal derived from the level gauge 2. 5 designates a duct network of a distributing area. As for pump start/stop, pump start is lagged 30 min. to correspond to flow-change time of a chlorine injection equipment 10, and pump stop is lagged 30 min. to correspond to flow-change time thereof.
The distributing reservoir of the water distributing installation needs to provide the cushioning function of water delivery and time variations. The simplest control of the water level of the distributing reservoir is control at the constant water level which is, however, practically ineffective in cushioning function. Though control at a target water level set every hour which considers time variations in water distribution obtains a certain result, it frequently produces a day where a result is unsatisfactory due to the fact that the distribution pattern is not constant every day. In view of an accident which occurs upstream of the distributing reservoir, the distributing reservoir needs to provide a water storage/distribution capacity. In order to fully meet this requirement, the water level of the distributing reservoir is always determined to a higher value within the range of effective depth. However, the water level needs to vary to some degree to meet the requirement of the cushioning function, and it needs to keep a higher constant value to meet the requirement upon occurrence of an accident.
Control is required which can satisfactorily adjust those requirements conflicting with each other. However, such ideal control is not achieved yet.
Moreover, with the above controls, increased number of times of pump start/stop causes damage to the installation and devices, resulting in lowered durability thereof.
It is, therefore, an object of the present invention to provide water distributing installation controllers which allow efficient control of water distribution and improved durability of the devices.